Concrete blocks may be formed with textured sides which may have undercuts. Because of the irregular surfaces, these blocks are not easily released from the form cavity in which they are cast. The shapes of the form cavity walls are such that the cured concrete block is locked within the form, even if the form is inverted. One method for releasing blocks with irregular surfaces from the form cavity is to hinge the side walls of the cavity so that the form walls may be pivoted away from the cast block after the concrete has sufficiently cured. This allows the block to be lifted from the form. Another method is to provide form walls which can be manually disassembled and separated from the block after it has cured, and reassembled for casting another block. The manual labor required to release or move the form sides from each block so that it can be removed from the form adds to the cost for manufacturing the blocks. It has been particularly difficult to manufacture large concrete blocks having highly irregular surfaces which have the appearance of natural stone. It is desirable to form some surfaces of the blocks with deep undercuts which imitate natural characteristics of stone.